Lubricating oil for use in hot-rolling oil and method for manufacturing hot-rolled sheet

ABSTRACT

A lubricating oil for use in hot-rolling oil for aluminum sheet, comprises: (a) a mineral oil having a kinematic viscosity of 80 mm 2 /second or less at 40° C.; (b) 1 to 14 mass % of a fatty acid having 10 to 22 carbon atoms; (c) 5 to 15 mass % of an oil and fat and/or a synthetic ester; (d) 5 to 10 mass % of a phosphorus-containing extreme-pressure agent; (e) 0.1 to 1 mass % of a polyoxyethylene alkyl amine; and 0.1 to 10 mass % of an organic acid salt of a copolymer composed of a (meth)acrylic acid salt, (meth)acrylamide, and at least one amine monomer, and the mass ratio of the component (c) to the component (d) (component (c)/component (d)) is 1/0.6 to 1/1. The lubricating oil for use in hot-rolling oil for aluminum sheet of the invention provides a high level of rolling lubricity, iron corrosion protection in a hot-rolling step and a rolled aluminum sheet with high sheet surface quality can be obtained.

TECHNICAL FIELD

The invention relates to a lubricating oil for use in hot-rolling oil for aluminum sheet. The invention also relates to a hot-rolling oil produced with the lubricating oil for use in hot-rolling oil. The invention also relates to a method for manufacturing a hot-rolled aluminum sheet with the hot-rolling oil. In the method for manufacturing a hot-rolled sheet, the hot-rolling oil is used, for example, in a rough rolling process in which strip rolling is performed. The term “aluminum sheet” of “for aluminum sheet”, which refers to use in an embodiment of the invention, is intended to include “pure aluminum sheet and/or aluminum alloy sheet.”

BACKGROUND ART

In general, an aluminum sheet is manufactured by a process including hot-rolling a slab, which has undergone melting, casting, facing, and homogenizing, into a sheet, then optionally subjecting the sheet to cold rolling, annealing, and conditioning steps (such as a step of slitting the sheet into a width of an appropriate product size and a reforming step for smooth flatness), and optionally performing a surface treatment process. Among the manufacturing steps, the hot-rolling step is most important for the quality of the aluminum sheet product. The hot-rolling step is performed using a method including performing rough rolling with a reverse-type hot roughing mill (rougher) and then performing finish rolling with a tandem-type hot finish rolling mill (finisher) or a method including performing both rough rolling and finish rolling with a single rolling mill for both rough rolling and finish rolling.

When an aluminum sheet is hot-rolled, aluminum is transferred and deposited onto the surface of the rolling mill roll from the surface of the sheet being rolled so that a roll coating is formed. Since the sheet being rolled is in contact with the roll coating, the surface quality of the rolled sheet depends on the properties of the roll coating. Surface defects formed on a sheet during hot-rolling also affect the sheet surface quality after cold rolling, which also means that the properties of the roll coating during hot-rolling is very important. The properties of the roll coating vary with various rolling conditions (such as sheet material, sheet temperature, sheet surface roughness, roll temperature, roll surface roughness, rolling reduction, rolling speed, and brush roll process conditions) and hot-rolling oil. Therefore, the selection of hot-rolling oil is indispensable for controlling the roll coating.

Hot-rolling oil is used in the form of an emulsion, because hot-rolling requires sufficient roll-cooling ability. Properties required of aluminum sheet hot-rolling oil include rolling lubricity, roll coating properties, sheet surface quality, emulsion stability, iron corrosion protection, etc. Conventionally, general aluminum sheet hot-rolling oil is used in the form of an emulsion which is prepared by mixing mineral oil as lubricating base oil with an oiliness improver such as a fatty acid, natural oil and fat, or a fatty acid ester, and other additives such as an extreme-pressure agent, an anticorrosive, and an antioxidant, and emulsifying the mixture generally with an anionic surfactant.

Unfortunately, in conventional hot-rolling oil for aluminum sheet produced with an emulsifying agent, rolling lubricity and emulsion stability tend to trade off against each other, and it has been impossible to achieve a satisfactory level of both performances. Specifically, when rolling lubricity is increased, emulsion stability decreases, so that the time-course stability of rolling lubricity also decreases, which causes a problem with the stability of aluminum sheet surface quality. On the other hand, when emulsion stability is increased, rolling lubricity cannot be obtained sufficiently, so that various defects are formed on aluminum sheet surfaces.

To ensure such mutually contradictory properties including rolling lubricity, emulsion stability and sheet surface quality at the same time, there is proposed a hot-rolling oil composition including a combination of a specific lubricating oil component and a specific water-soluble cationic polymer compound (Patent Document 1). There is also proposed a hot-rolling oil in which a specific lubricating oil component is used in combination with an anionic surfactant and an nonionic surfactant (Patent Document 2).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP No. 2869850

Patent Document 2: JP No. 2990021

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In recent years, high quality and low cost aluminum rolled products have been demanded, and therefore there has been a demand for hot-rolling oil that makes it possible to obtain more stable rolling lubricity and sheet surface quality. For example, a study has been conducted on methods for manufacturing mainly 3xxx aluminum alloy-based materials for beverage can bodies or the like or 1xxx pure aluminum materials for printing plates or the like in which annealing is omitted for cost reduction, and a manufacturing method in which the aluminum structure, which controls the formability of aluminum sheet products or the appearance characteristics of aluminum sheet products after surface treatment, is optimized by a hot-rolling process rather than an annealing process so that quality characteristics can also be improved is going mainstream. A proper structure should be formed in the hot-rolling process so that a proper structure can be formed in final products. For this purpose, the hot-rolling conditions become severe, because high reduction techniques or high strain rate techniques or the like are required as compared with conventional techniques, and therefore surface anomalies such as seizing tend to be more likely to occur due to insufficient lubricity. Therefore, the hot-rolling oil to be used is required to have higher lubricity than conventional oils. If the lubricity of hot-rolling oil can be improved, a reduction in the number of rough hot-rolling passes or an increase in productivity by increasing the rolling speed can be expected even using high-Mg aluminum alloy sheets (5xxx aluminum alloys such as 5182 aluminum alloy for beverage can lids), which have high deformation resistance and therefore conventionally make it difficult to reduce the number of rough hot-rolling passes due to insufficient lubricity. On the other hand, when the aluminum material to be rough hot-rolled has low deformation resistance, care should be taken not to degrade biting performance, particularly, not to degrade performance in biting a pure aluminum sheet whose coefficient of friction is low during rolling. Therefore, hot-rolling oil for aluminum sheet is also required to satisfy these mutually contradictory requirements.

According to Patent Document 1, the amount of a fatty acid, which is one of the lubricating oil components and serves as an oiliness improver, may be increased. However, if the content of the fatty acid in the hot-rolling oil composition is increased to 15 mass % or more, a problem will occur in which the fatty acid has considerably high corrosiveness, and there will be a further problem in which metal soap, which is a high-viscosity material, is produced as rolling proceeds, so that the area around the rolling mill is soiled with the metal soap.

Patent Document 2 proposes a technique to improve rolling lubricity with no degradation in iron corrosion protection, in which hot-rolling oil with improved rolling lubricity is prepared using a relatively large amount of natural oil and fat and/or a synthetic ester so that the content of a fatty acid can be limited. In a rough rolling process where strip rolling is performed, however, an increase in rolling lubricity may lead to reductions in biting performance and operating performance. In addition, the proposed technique does not improve the surface quality of aluminum alloy sheets.

An object of the invention is to provide a lubricating oil for use in hot-rolling oil for aluminum sheet, which provides a high level of rolling lubricity, iron corrosion protection and biting performance and makes it possible to obtain a rolled aluminum sheet with high sheet surface quality, even under severe hot-rolling conditions where the reduction and/or the strain rate is set high as compared with conventional processes.

Another object of the invention is to provide a hot-rolling oil produced with the lubricating oil for use in hot-rolling oil. A further object of the invention is to provide a method for manufacturing a hot-rolled aluminum sheet with the hot-rolling oil.

Means for Solving the Problems

Specifically, the invention is directed to a lubricating oil for use in hot-rolling oil for aluminum sheet, including:

(a) a mineral oil having a kinematic viscosity of 80 mm²/second or less at 40° C.;

(b) 1 to 14 mass % of a fatty acid having 10 to 22 carbon atoms;

(c) 5 to 15 mass % of an oil and fat and/or a synthetic ester;

(d) 5 to 10 mass % of a phosphorus-containing extreme-pressure agent;

(e) 0.1 to 1 mass % of a polyoxyethylene alkyl amine; and

-   -   (f) 0.1 to 10 mass % of an organic acid salt of a copolymer         composed of a (meth)acrylic acid salt, (meth)acrylamide, and at         least one amine monomer represented by formula (1):

wherein R¹ represents a hydrogen atom or a methyl group, R² and R³ represent the same or different alkyl groups of 1 to 3 carbon atoms, A represents —NH—, and m represents an integer of 1 to 3, wherein

the organic acid salt of the copolymer has a weight average molecular weight of 10,000 to 1,000,000,

-   -   an organic acid used to form the organic acid salt of the         copolymer is represented by formula (2): R⁴COOH, wherein R⁴         represents an alkyl group of 1 to 5 carbon atoms, a hydroxyalkyl         group of 1 to 5 carbon atoms, a carboxyalkyl group with an alkyl         moiety of 1 to 5 carbon atoms, or a carboxyl group, and

the mass ratio of the component (c) to the component (d) (component (c)/component (d)) is 1/0.6 to 1/1.

The invention is also directed to an aluminum sheet hot-rolling oil including the above lubricating oil for use in hot-rolling oil and water.

The invention is also directed to a method for manufacturing a hot-rolled sheet, including a step of hot-rolling an aluminum sheet in the presence of the above aluminum sheet hot-rolling oil.

Effects of the Invention

In a hot-rolling step of a rolled aluminum sheet-manufacturing process, particularly in a rough hot-rolling step where strip rolling is performed, the hot-rolling oil produced with the lubricating oil for use in hot-rolling oil for aluminum sheet of the invention (hereinafter referred to as “the lubricating oil for use in hot-rolling oil of the invention”) provides a high level of rolling lubricity and iron corrosion protection, maintains biting performance, and makes it possible to obtain a rolled aluminum sheet with high sheet surface quality, even under severe hot-rolling conditions where the reduction and/or the strain rate is set high as compared with conventional processes.

The hot-rolling oil composition disclosed in Patent Document 1 also contains components similar to those of the lubricating oil for use in hot-rolling oil of the invention. However, the hot-rolling oil composition disclosed in Patent Document 1 does not completely satisfy the requirements for the recent demand for high quality and low cost products under severe hot-rolling conditions where the reduction and/or the strain rate is set high for the production of high quality and low cost products, although it can somewhat ensure both rolling lubricity and sheet surface quality under conventional aluminum sheet hot-rolling conditions. In general, the amount of an oil and fat or a synthetic ester may be increased so that rolling lubricity can be improved. However, when the amount of the oil and fat or the synthetic ester is increased, the coefficient of friction is reduced, and in particular, performance in biting a pure aluminum sheet is degraded. The phosphorus-containing extreme-pressure agent can increase the sheet surface quality with no increase in rolling lubricity, but the phosphorus-containing extreme-pressure agent is expensive and therefore cannot be used in a large amount. The fatty acid is effective for rolling lubricity and sheet surface quality, but it degrades iron corrosion protection when used in a large amount. Thus, the content of each component in the lubricating oil for use in hot-rolling oil is restricted. The lubricating oil for use in hot-rolling oil of the invention contains components similar to those of the hot-rolling oil composition disclosed in Patent Document 1. In the lubricating oil for use in hot-rolling oil of the invention, however, the content of the oil and fat or the synthetic ester and the content of the phosphorus-containing extreme-pressure agent or the like are not increased, whereas the content of the oil and fat or the synthetic ester is controlled to be equal to or slightly higher than the content of the phosphorus-containing extreme-pressure agent, so that the lubricating oil for use in hot-rolling oil of the invention can ensure both rolling lubricity and sheet surface quality and further provide a satisfactory level of iron corrosion protection and biting performance even under severe hot-rolling conditions where the reduction and/or the strain rate is set high for the production of aluminum sheets with high level characteristics, which have been demanded in recent years.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the lubricating oil for use in hot-rolling oil of the invention, the mineral oil as the component (a) is typically a spindle oil, a machine oil, a turbine oil, a cylinder oil, a neutral oil, or the like. In view of heat resistance and rolling lubricity, these mineral oils are more preferably paraffinic mineral oils. The mineral oil to be used has a viscosity of 80 mm²/second or less at 40° C. If the viscosity exceeds 80 mm²/second, sheet surface quality may be reduced. The component (a) is a base oil of the lubricating oil for use in hot-rolling oil of the invention. The component (a) to be used may be a single oil or a combination of two or more oils. While the content of the component (a) in the whole of the lubricating oil for use in hot-rolling oil is 88.8 mass % or less, it is preferably from 51 to 88.8 mass %, more preferably from 60 to 85 mass %, even more preferably from 65 to 80 mass % in view of rolling lubricity, iron corrosion protection, sheet surface quality, or biting performance.

The fatty acid having 10 to 22 carbon atoms as the component (b) may be capric acid, lauric acid, stearic acid, isostearic acid, oleic acid, erucic acid, palm oil fatty acid, or the like. In view of rolling lubricity, emulsion stability, iron corrosion protection, or sheet surface quality, the fatty acid preferably has 10 to 20 carbon atoms, more preferably 13 to 20 carbon atoms, further the fatty acid is preferably an unsaturated or branched fatty acid having 13 to 20 carbon atoms. The component (b) acts as an oiliness improver, which may be a single fatty acid or a combination of two or more fatty acids. In view of emulsion stability, oleic acid and isostearic acid are preferred, and oleic acid is more preferred, because they are liquid and non-precipitable at room temperature. The content of the component (b) in the whole of the lubricating oil for use in hot-rolling oil of the invention is from 1 to 14 mass %, preferably from 2 to 12 mass %, more preferably from 4 to 10 mass %. Controlling the content of the component (b) in the above range is preferred in view of rolling lubricity, emulsion stability, iron corrosion protection, or sheet surface quality.

An oil and fat and/or a synthetic ester is used as the component (c). The oil and fat is a naturally occurring ester, and the synthetic ester is an artificially produced ester. Examples of the oil and fat include animal and vegetable oils and fats such as whale oil, beef tallow, lard, rapeseed oil, castor oil, palm oil, and coconut oil. The synthetic ester may be a synthetic ester (1) derived from a fatty acid and a monohydric or polyhydric alcohol. The fatty acid may be a fatty acid having 10 to 22 carbon atoms, examples of which include those listed for the component (b) and fatty acids derived from the oils and fats. The monohydric alcohol may be a monohydric fatty alcohol having 1 to 22 carbon atoms. In view of sheet surface quality, a fatty alcohol having 1 to 15 carbon atoms is preferred, and a fatty alcohol having 1 to 8 carbon atoms is more preferred. Examples of the polyhydric alcohol include ethylene glycol, trimethylolpropane, pentaerythritol, and glycerin. The synthetic ester (1) is preferably a fatty acid monoester, examples of which include methyl caprate, butyl stearate, laurate oleate, 2-ethylhexyl erucate, pentaerythritol monooleate, and glycerin monooleate. The synthetic ester may also be a synthetic ester (2) derived from a fatty alcohol and a monobasic or polybasic acid. The fatty alcohol may be a fatty alcohol having the same number of carbon atoms as the fatty acid having 10 to 22 carbon atoms. In view of sheet surface quality, a fatty alcohol having 10 to 20 carbon atoms is preferred, and a fatty alcohol having 12 to 18 carbon atoms is more preferred. Examples of the polybasic acid include phthalic acid, trimellitic acid, adipic acid, and sebacic acid. Examples of the synthetic ester (2) include dilauryl phthalate, tri-2-ethylhexyl trimellitate, diisodecyl adipate, and dioleyl sebacate. The component (c) to be used may be a single ester or a combination of two or more esters. In view of sheet surface quality, the component (c) is preferably the synthetic ester, more preferably the synthetic ester (1), even more preferably a fatty acid monoester, still more preferably butyl stearate. The component (c) acts as an oiliness improver, and the content of the component (c) in the whole of the lubricating oil for use in hot-rolling oil of the invention is preferably from 5 to 15 mass %, more preferably from 6 to 15 mass %. Controlling the content of the component (c) in the above range is preferred in view of rolling lubricity, sheet surface quality, or biting performance.

An extreme-pressure agent provides rolling lubricity without reducing the coefficient of friction during rolling. Examples of the phosphorus-containing extreme-pressure agent as the component (d) include alkyl or alkenyl phosphates or alkyl or alkenyl phosphites. In view of rolling lubricity and sheet surface quality, the phosphorus-containing extreme-pressure agent is preferably an alkyl or alkenyl phosphate or an alkyl or alkenyl phosphite. The alkyl or alkenyl group of the phosphate or the phosphite may have 4 to 18 carbon atoms, and examples of the phosphate and the phosphite include dibutyl phosphate, monooctyl phosphate, trioleyl phosphate, tricresyl phosphate, tributyl phosphite, diisooctyl phosphite, trioleyl phosphite, and triisooctyl phosphite. In view of sheet surface quality, the number of the carbon atoms is preferably from 4 to 15, more preferably from 4 to 8. The phosphate or phosphite may be a monoester, diester or triester. In view of iron corrosion protection, an alkyl or alkenyl acid phosphate or an alkyl or alkenyl acid phosphite, which is a triester, is preferred. The component (d) to be used may be a single agent or a combination of two or more agents. The content of the component (d) in the whole of the lubricating oil for use in hot-rolling oil of the invention is preferably from 5 to 10 mass %, more preferably from 6 to 10 mass %, even move preferably from 8 to 10 mass %. Controlling the content of the component (d) in the above range is preferred in view of rolling lubricity or sheet surface quality.

The component (c) and the component (d) are used in a component (c)/component (d) mass ratio of 1/0.6 to 1/1. The mass ratio is preferably 1/0.7 to 1/1, more preferably 1/0.8 to 1/1. Controlling the ratio of the component (c) to the component (d) in the above range is preferred in view of sheet surface quality and biting performance.

The polyoxyethylene alkyl amine as the component (e) may be a compound represented by formula (3): R⁵—NH-(EO)_(n)—H or formula (4): H-(EO)_(n1)—NR⁶-(EO)_(n2)—H, wherein R⁵ and R⁶ each represent an alkyl group of 10 to 18 carbon atoms, preferably an alkyl group of 10 to 16 carbon atoms, more preferably an alkyl group of 12 to 14 carbon atoms in view of emulsion stability and iron corrosion protection, EO represents an oxyethylene group, n, n1, and n2 each represent an average addition mole number of EO, n is preferably from 2 to 10, more preferably from 2 to 8, even more preferably from 2 to 5 in view of emulsion stability and iron corrosion protection, n1 and n2 are each 1 or more, and n1+n2 is preferably from 2 to 10, more preferably from 2 to 8, even more preferably from 2 to 5 in view of emulsion stability and iron corrosion protection. The component (e) acts as an anticorrosive. The component (e) to be used may be a single compound or a combination of two or more compounds. In view of emulsion stability and iron corrosion protection, the component (e) is preferably polyoxyethylene lauryl amine. The content of the component (e) in the whole of the lubricating oil for use in hot-rolling oil of the invention is from 0.1 to 1 mass %, preferably from 0.2 to 1 mass %, more preferably from 0.4 to 1 mass %. Controlling the content of the component (e) in the above range is preferred in view of emulsion stability or iron corrosion protection. In view of emulsion stability and iron corrosion protection, the component (e) preferably has an HLB of 6 to 13, more preferably 10 to 13.

The organic acid salt of the copolymer as the component (f) is an organic salt composed of a copolymer of an amine monomer represented by formula (1), (meth)acrylamide, and a (meth)acrylic acid salt. The term “(meth)acrylamide” refers to acrylamide and/or methacrylamide, and the term “(meth)acrylic acid salt” refers to acrylic acid salt and/or methacrylic acid salt. In the description, “(meth)” has the same meaning as mentioned above. In the copolymer of the amine monomer represented by formula (1), (meth)acrylamide, and the the (meth)acrylic acid salt, the molar ratio (amine monomer:(meth)acrylamide:(meth)acrylic acid salt) is preferably 50-90:0.1-20:10-50, more preferably 59-90:1-10:10-30, even more preferably 69-90:1-5:10-25 in view of emulsion stability.

Examples of the amine monomer represented by formula (1) include dimethylaminoethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, and diethylaminomethyl(meth)acrylamide. Among the examples, dimethylaminopropylmethacrylamide and diethylaminopropylacrylamide are preferred in view of emulsion stability.

Examples of the (meth)acrylic acid salt include (meth)acrylic acid alkali metal salt such as sodium salt of (meth)acrylic acid and potassium salt of (meth)acrylic acid; and (meth)acrylic acid organic amine salts, such as monoethanolamine salt of (meth)acrylic acid, diethanolamine salt of (meth)acrylic acid, and triethanolamine salt of (meth)acrylic acid.

The organic acid used to form the organic acid salt of the copolymer as the component (f) includes a compound represented by formula (2): R⁴COOH, which provides R⁴COO⁻ to form an organic acid salt with the amino group of the amine monomer represented by formula (1). Examples of R⁴ in the formula include an alkyl group of 1 to 5 carbon atoms, a hydroxyalkyl group of 1 to 5 carbon atoms, a carboxyalkyl group with an alkyl moiety of 1 to 5 carbon atoms, and a carboxyl group. In view of emulsion stability, R⁴ is preferably a methyl group or a hydroxyalkyl group of 1 to 5 carbon atoms. Examples of R⁴COO— include acetate ion, propionate ion, butyrate ion, valerate ion, caproate ion, glycolate ion, lactate ion, hydroacrylate ion, oxalate ion, malonate ion, succinate ion, glutarate ion, and adipate ion. Among them, acetate ion, glycolate ion, lactate ion, and hydroacrylate ion are preferred, and acetate ion and glycolate ion are more preferred in view of emulsion stability.

The organic acid salt of the copolymer as the component (f) preferably has a weight average molecular weight in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 300,000. When having a weight average molecular weight in the above range, the organic acid salt of the copolymer provides good emulsion stability ad has good handleability. The weight average molecular weight may be determined by a process including adding 10 ml of 0.5 M sodium hydroxide to 1 g of the organic acid salt of the copolymer, allowing the mixture to stand at 95° C. for 2 hours to perform hydrolysis, then measuring the molecular weight by GPC (gel permeation chromatography), and calculating the molecular weight before the hydrolysis based on the result. Specifically, the GPC conditions are as follows:

-   Column: α-M×2 (manufactured by TOSOH CORPORATION) -   Column temperature: 40° C. -   Eluent: 0.15 M sodium sulfate, 1% acetic acid aqueous solution -   Detector: RI (differential refractometer) -   Injection volume: 0.5% (wt/vol) eluent aqueous solution, 100 μl -   Flow rate: 1.0 ml/minute -   Molecular weight standard: Pullulan (manufactured by SHODEX Inc.)     (four standards of 788,000, 194,000, 46,700, and 5,900)

For example, the organic acid salt of the copolymer as the component (f) may be obtained by neutralizing the produced copolymer with the organic acid of formula (2) or by previously neutralizing the amine monomer represented by formula (1) with the organic acid of formula (2) in the production of the copolymer.

The component (f) to be used may be a single salt or a combination of two or more salts. The content of the component (f) in the whole of the lubricating oil for use in hot-rolling oil of the invention is from 0.1 to 10 mass %, preferably from 0.4 to 5 mass %, more preferably from 0.6 to 3 mass %. Controlling the content of the component (f) in the above range is preferred in view of rolling lubricity or sheet surface quality.

Besides the above components, if necessary, the lubricating oil for use in hot-rolling oil of the invention may further contain known additives such as an anticorrosive, an antioxidant, and an emulsifying agent for improving initial emulsifiability.

Examples of the anticorrosive that may be used include alkenyl succinate and derivatives thereof, fatty acids such as oleic acid, esters such as sorbitan monooleate, and other amines. The content of the anticorrosive in the whole of the lubricating oil for use in hot-rolling oil of the invention is preferably from 0.2 to 2 mass %, more preferably from 0.5 to 1.5 mass %.

Examples of the antioxidant that may be used include phenolic compounds such as 2,4-di-tert-butyl-p-cresol and aromatic amines such as phenyl-α-naphthylamine. The antioxidant is preferably added in an amount of 0.2 to 5 mass %, more preferably 0.5 to 1.5 mass %, based on the total mass of the lubricating oil for use in hot-rolling oil of the invention.

Examples of the emulsifying agent that may be used include anionic surfactants such as triethanolamine salt of oleic acid and sodium petroleum sulfonate and nonionic surfactants such as polyoxyethylene lauryl ether. The content of the emulsifying agent is preferably 2 mass % or less, more preferably 1 mass % or less, based on the total mass of the lubricating oil for use in hot-rolling oil of the invention.

The lubricating oil for use in hot-rolling oil of the invention is diluted with water when used to form a hot-rolling oil. The water dilution is a hot-rolling oil emulsion (O/W type emulsion) containing the lubricating oil for use in hot-rolling oil of the invention dispersed in water. The dilution rate with water to form the water dilution is not restricted. In general, the concentration of the lubricating oil for use in hot-rolling oil of the invention in the water dilution is preferably from 1 to 30 mass %, more preferably from 2 to 15 mass %. In the hot-rolling oil emulsion, the emulsion particles preferably has a volume average particle size of 1 to 20 μm, more preferably 5 to 15 μm in view of rolling lubricity and emulsion stability.

The hot-rolling oil of the invention is to be used in the process of rolling an aluminum sheet with a hot-rolling mill in a method for manufacturing a hot-rolled sheet. The rolling process may be performed using conventional methods (see for example “Keikinzoku no Kenkyu to Gijutsu no Ayumi,” (History of Research and Technology of Light Metals) published on Nov. 30, 1991 by The Japan Institute of Light Metals), examples of which include a rough rolling process in which strip rolling is performed, and a finish rolling process in which coil rolling is performed. A conventionally-used rolling oil supply system (see for example “Keikinzoku no Kenkyu to Gijutsu no Ayumi,” (History of Research and Technology of Light Metals) published on Nov. 30, 1991 by The Japan Institute of Light Metals) may be used in a method of supplying the hot-rolling oil of the invention to the hot-rolling process, and examples of such a method include methods of applying an emulsion of the hot-rolling oil to a rolling mill roll with a spray or the like. Specifically, the method of the invention for manufacturing a hot-rolled sheet includes the step of hot-rolling an aluminum sheet in the presence of the aluminum sheet hot-rolling oil of the invention. The method described above may be used to supply the aluminum sheet hot-rolling oil of the invention to the hot-rolling step.

EXAMPLES Examples 1 to 8 and Comparative Examples 1 to 6

Hot-rolling oils (O/W type emulsions) with a concentration of 2 mass % were prepared under the conditions described below using water and different lubricating oils for use in hot-rolling oil with the compositions shown in Table 1 for hot-rolling oils. The hot-rolling oil of Comparative Example 3 corresponds to the No. 3 blend in Examples according to the invention disclosed in Patent Document 1.

(Conditions for Preparation of Hot-Rolling Oil Emulsions)

Fluid temperature: 60° C.

Mixer: M-type homomixer (manufactured by PRIMIX Corporation)

Number of revolutions: 8,000 r/minute

(Conditions for Measurement of Volume Average Particle Size of Hot-Rolling Oil Emulsion Particles)

Measuring instrument: Coulter Counter Multisizer (manufactured by Beckman Coulter, Inc.)

Measurement temperature: 25° C.

Dilution conditions: 30 μl was taken from each of the prepared hot-rolling oils and diluted to 100 ml with a dilution solution for blood (manufactured by Wako Pure Chemical Industries, Ltd.), when the volume average particle size was measured.

The hot-rolling oils were subjected to the test examples described below in which lubricity in rolling of an aluminum alloy sheet, sheet surface quality, iron corrosion protection, and biting performance were evaluated.

Test Example 1

Using each of the prepared hot-rolling oils, a strip rolling process (single pass) was performed with a two-high rolling mill (200 mmφ×200 mm width, SUJ-2, Hs=60) under the conditions shown below. The hot-rolling oil emulsion was supplied to the hot-rolling process by spraying it on the rolling mill roll.

(Rolling Conditions)

Material to be rolled: Aluminum alloy material (A5182, 40 mm wide×700 mm long×3.3 mm thick)

Roll roughness: Polishing was performed in the rolling direction with abrasive paper so that the roughness in the sheet width direction could be adjusted to Ra=0.3-0.4 μm (Rz=3.5-4.0 μm).

Sheet temperature: 510° C.

Rolling speed: 40 m/minute

Rolling reduction: 45% (average for four pieces)

Pre-rolling: A pure aluminum material (A1100, 40 mm wide×700 mm long×3.5 mm thick) was previously rolled at a rolling reduction of 70%.

(Conditions for Supply of Hot-Rolling Oil Emulsion)

Spray rate: 2 L/minute×one for each of the upper and lower parts, 200 kPa

<Rolling Lubricity (Rolling Test)>

The rolling load at a rolling reduction of 45% was used to evaluate the rolling lubricity. The test was performed four times using each hot-rolling oil, and the average was used as an index of the rolling lubricity. When the rolling load is 430 MPa or less, the rolling lubricity is good. The results are shown in Table 1. The rolling load indicates the surface pressure calculated from: the average of loads measured with a load cell in the two-high rolling mill during the rolling; and the contact area calculated from the sheet thicknesses before and after the rolling.

<Biting Performance (Rolling Test)>

The coefficient of friction during the pre-rolling was used to evaluate “performance in biting” a pure aluminum sheet. The test was performed four times using each hot-rolling oil, and the average was used as an index of the biting performance. When the coefficient of friction is 0.16 or more, the biting performance is good. The results are shown in Table 1.

The coefficient of friction was determined by a process including performing a rolling process using a work roll with projection marks, measuring the transferred mark pitch (the distance between the marks) on the rolled material (the surface of the rolled sheet), calculating a forward slip from the distance L1 between the specific projection marks on the rolling mill roll, and calculating the coefficient of friction from the formulae below.

μ=0.5×[(h1−h2)/R2]^(0.5)/{1−2×[(1−r)×δ/r] ^(0.5)},

wherein μ represents the coefficient of friction, h1 the sheet thickness (mm) before rolling, h2 the sheet thickness (mm) after rolling, R2 the flattened roll diameter (mm), r the rolling reduction, and δ the forward slip.

R2=R×{1+16×(1−ν²)×P/[π×E×b×(h1−h2)]},

wherein R represents the roll diameter, ν the Poisson's ratio, P the rolling load, E the Young's modulus, and b the sheet width.

r=(h1−h2)/h1

δ=(L1−L2)/L1, wherein L1 represents the distance (mm) between the projections (marks) on the rolling mill roll, and L2 represents the distance (mm) between the marks transferred onto the rolled sheet.

According to an embodiment of the invention, the test was performed using the following specific values: h1=3.5 mm, r=0.7, R=100 mm, b=40 mm.

Since the roll is made of iron, ν and E are 0.3 and 20,000, respectively, which are values specific to iron.

Test Example 2 Sheet Surface Quality (Alumite Test)

The rolled sheet obtained in Test Example 1 was subjected to an alumite treatment under the conditions shown below, and the surface of the rolled sheet after the alumite treatment was measured for whiteness degree, when the sheet surface quality was evaluated. The test was performed four times using each hot-rolling oil, and the average was used as an index of the sheet surface quality. When the whiteness degree shown below is evaluated to be 4 or more, the sheet surface quality is good. The results are shown in Table 1.

(Test Conditions)

Treatment solution: An aqueous 15 w/v % sulfuric acid solution

Treatment temperature: 20° C.

Current density: 2 A/dm²

Treatment time: 20 minutes

Cleaning method: Immersion in tap water flowing at 2 L/minute for 10 minutes was followed by washing with ion-exchanged water.

(Measurement Conditions)

Measuring equipment: spectroscopic colorimeter SE-2000 (manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.)

Measurement item: Whiteness degree WB

Evaluation Method (in the case of A5182)

The evaluation was performed according to the criteria below. The higher the whiteness degree WB, the better the sheet surface quality.

-   5: The whiteness degree WB is 34 or more. -   4: The whiteness degree WB is from 30 to less than 34. -   3: The whiteness degree WB is from 24 to less than 30. -   2: The whiteness degree WB is from 20 to less than 24. -   1: The whiteness degree WB is less than 20.

Test Example 3 Iron Corrosion Protection

Each prepared hot-rolling oil was subjected to a corrosion test under the conditions shown below, and the corrosion rate (mg/m²·day) was used to evaluate the iron corrosion protection. The test was performed four times using each hot-rolling oil, and the average was used as an index of the iron corrosion protection. When the corrosion rate is 200 mg/m²·day or less, the iron corrosion protection is good. The results are shown in Table 1. The corrosion rate was determined by a process including measuring the mass of the test piece with a precision balance before and after the test and calculating the corrosion rate from the reduction in the mass and the area of the test piece.

(Test Conditions)

Test piece: SS-400 sheet (3 mm thick×50 mm×50 mm)

Pretreatment: The test piece was polished with #240 polishing paper and then degreased with a solvent.

Immersion method: The test piece was entirely immersed in each hot-rolling oil under stirring with an M-type homomixer at 6,000 r/minute.

Testing temperature: 60° C.

Testing time: 3 days.

TABLE 1 Example 1 2 3 4 5 6 7 8 Lubricating Component Mineral oil A 73.7 79.6 73.6 73.6 73.6 73.6 66.1 75.6 oil for use (a) Mineral oil B — — — — — — — — in hot- Component Fatty acid A 10.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 rolling oil (b) for aluminum Component Oil and fat A 6.0 6.0 — — — — 5.0 — sheet (c) Oil and fat B — — 10.0 — — — — — (mass %) Ester A — — — 10.0 — — 10.0 10.0 Ester B — — — — 10.0 — — — Ester C — — — — — 10.0 — — Component Extreme-pressure 6.0 6.0 8.0 8.0 8.0 8.0 — 6.0 (d) agent A Extreme-pressure — — — — — — 10.0 — agent B Component Anticorrosive A 0.8 0.4 0.4 0.4 0.4 0.4 0.4 0.4 (e) Component Organic salt of 1.0 1.0 — — — — 1.0 — (f) copolymer A Organic salt of — — 1.0 1.0 1.0 1.0 — 1.0 copolymer B Others Additive A 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Additive B 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Additive C 0.5 — — — — — 0.5 — Additive D — — — — — — — — Additive E — — — — — — — — Mass ratio of component (c)/component (d) 1/1 1/1 1/0.8 1/0.8 1/0.8 1/0.8 1/0.66 1/0.6 Evaluations Volume average particle size 8 8 10 10 10 10 8 9 of rolling (μm) oils Rolling lubricity 400 410 400 410 400 400 400 410 (MPa) Biting performance 0.17 0.18 0.18 0.18 0.18 0.18 0.17 0.18 (friction coefficient) (Evaluation) ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Sheet surface quality (whiteness 32 32 33 34 33 33 34 33 degree) (Evaluation) 4 4 4 5 4 4 5 4 Iron corrosion protection 170 100 100 100 100 100 100 100 (mg/m² · day) Comparative example 1 2 3 4 5 6 Lubricating Component Mineral oil A — — 77.0 41.0 70.6 68.6 oil for use (a) Mineral oil B 59.5 39.5 — — — — in hot- Component Fatty acid A 20.0 6.0 5.0 5.0 5.0 5.0 rolling oil (b) for aluminum Component Oil and fat A — 25.0 — 15.0 — — sheet (c) Oil and fat B 10.0 — — — — — (mass %) Ester A — — 10.0- — 15.0 10.0 Ester B — — — — — — Ester C — 25.0 — 15.0 — 5.0 Component Extreme-pressure 2.5 — — 6.0 6.0 8.0 (d) agent A Extreme-pressure — — 5.0 — — — agent B Component Anticorrosive A — — — — 0.4 0.4 (e) Component Organic salt of — — — — — — (f) copolymer A Organic salt of — — 1.0 1.0 1.0 1.0 copolymer B Others Additive A 1.0 — 1.0 1.0 1.0 1.0 Additive B 1.0 — 1.0 1.0 1.0 1.0 Additive C 3.0 3.0 — — — — Additive D 3.0 1.5 — — — — Additive E — — — 15.0 — — Mass ratio of component (c)/component (d) 1/0.25 ∞ 1/0.5 1/0.2 1/0.4 1/0.53 Evaluations Volume average particle size 2 4 10 10 10 10 of rolling (μm) oils Rolling lubricity 510 460 410 380 390 400 (MPa) Biting performance 0.20 0.19 0.18 0.15 0.17 0.17 (friction coefficient) (Evaluation) ◯ ◯ ◯ X ◯ ◯ Sheet surface quality (whiteness 19 20 29 32 28 28 degree) (Evaluation) 1 2 3 4 3 3 Iron corrosion protection 460 170 490 150 150 100 (mg/m² · day)

In Table 1, the mineral oils, fatty acids, oils and fats, esters, extreme-pressure agents, anticorrosives, organic salts of copolymers, and other additives have the meanings shown below.

Mineral oil A: paraffinic mineral oil (with a kinematic viscosity of 30 mm²/second at 40° C.) (Super Oil K32 manufactured by Nippon Oil Corporation)

Mineral oil B: Naphthene-based mineral oil (with a kinematic viscosity of 30 mm²/second at 40° C.) (Diana Fresia N-28 manufactured by Idemitsu Kosan Co., Ltd.)

Fatty acid A: Oleic acid (LUNAC O-P manufactured by Kao Corporation)

Oil and fat A: Palm oil (RPO ACE manufactured by UEDA OILS AND FATS MFG CO., LTD.)

Oil and fat B: Lard (reagent manufactured by Kishida Chemical Co., Ltd.)

Ester A: Butyl stearate (EXCEPARL BS manufactured by Kao Corporation)

Ester B: Dilaurly phthalate (VINYCIZER 124 manufactured by Kao Corporatoin)

Ester C: Trimethylolpropane coconut oil fatty acid triester (ADDLUBE E-124 manufactured by Kao Corporation)

Extreme-pressure agent A: Tricresyl phosphate (DURAD TCP manufactured by AJINOMOTO CO., INC.)

Extreme-pressure agent B: Triisooctyl phosphite (JP-308E manufactured by Johoku Chemical Co., Ltd.)

Anticorrosive A: Polyoxyethylene lauryl amine (average EO addition of 5 moles, HLB=10.4) (AMIET 105 manufactured by Kao Corporation)

Organic acid salt of copolymer A: A product of neutralization of a copolymer of dimethylaminopropylacrylamide/acrylamide/sodium salt of acrylic acid (80/5/15) with acetic acid (with a weight average molecular weight of 100,000 synthesized in laboratory at a reaction temperature of 50° C. using a polymerization initiator and monomers manufactured by Wako Pure Chemical Industries, Ltd.)

Organic acid salt of copolymer B: A product of neutralization of a copolymer of dimethylaminopropylmethacrylamide/acrylamide/sodium salt of acrylic acid (84/1/15) with glycolic acid (with a weight average molecular weight of 50,000 synthesized in laboratory at a reaction temperature of 50° C. using a polymerization initiator and monomers manufactured by Wako Pure Chemical Industries, Ltd.)

Additive A: Rust-preventive agent (hexadecenyl succinate) (L-ASA manufactured by Kao Corporation)

Additive B: Antioxidant (2,6-di-tert-butyl-p-cresol) (YOSHINOX BHT manufactured by API Corporation)

Additive C: Polyoxyethylene lauryl ether (average BO addition of 7 moles, HLB=12.1) (EMULGEN 707 manufactured by Kao Corporation)

Additive D: Triethanolamine (reagent manufactured by Wako Pure Chemical Industries, Ltd.)

Additive E: Coconut oil-reduced alcohol (KALCOL 2455 manufactured by Kao Corporation)

Table 1 shows that hot-rolling oil emulsions prepared using lubricating oils for use in hot-rolling oil of the invention provide a satisfactory level of lubricity, sheet surface quality and iron corrosion protection in rolling of aluminum alloy sheets and a satisfactory level of performance in biting pure aluminum sheets and that comparative products that do not satisfy the features of the invention have a problem with at least one of the performances. Therefore, the lubricating oil for use in hot-rolling oil of the invention would also be effective for lubricity, sheet surface quality and iron corrosion protection in rolling of pure aluminum sheets and effective for performance in biting aluminum alloy sheets. 

1. A lubricating oil for use in hot-rolling oil for aluminum sheet, comprising: (a) a mineral oil having a kinematic viscosity of 80 mm²/second or less at 40° C.; (b) 1 to 14 mass % of a fatty acid having 10 to 22 carbon atoms; (c) 5 to 15 mass % of an oil and fat, a synthetic ester or a combination thereof; (d) 5 to 10 mass % of a phosphorus-containing extreme-pressure agent; (e) 0.1 to 1 mass % of a polyoxyethylene alkyl amine; and (f) 0.1 to 10 mass % of an organic acid salt of a copolymer having repeat units of a (meth)acrylic acid salt, (meth)acrylamide, and at least one amine monomer represented by formula (1):

wherein R¹ represents a hydrogen atom or a methyl group, R² and R³ represent the same or different alkyl groups of 1 to 3 carbon atoms, A represents —NH—, and m represents an integer of 1 to 3, wherein the organic acid salt of the copolymer has a weight average molecular weight of 10,000 to 1,000,000, where an organic acid used to form the organic acid salt of the copolymer is represented by formula (2): R⁴COOH   (2), wherein R⁴ represents an alkyl group of 1 to 5 carbon atoms, a hydroxyalkyl group of 1 to 5 carbon atoms, a carboxyalkyl group with an alkyl moiety of 1 to 5 carbon atoms, or a carboxyl group, and the mass ratio of the component (c) to the component (d) (component (c)/component (d)) is 1/0.6 to 1/1.
 2. The lubricating oil for use in hot-rolling oil for aluminum sheet according to claim 1, wherein the component (c) is butyl stearate.
 3. An aluminum sheet hot-rolling oil, comprising the lubricating oil for use in hot-rolling oil according to claim 1 and water.
 4. A method for manufacturing a hot-rolled sheet, comprising a hot-rolling an aluminum sheet in the presence of the aluminum sheet hot-rolling oil according to claim
 3. 5. An aluminum sheet hot-rolling oil, comprising the lubricating oil for use in hot-rolling oil according to claim 2 and water.
 6. A method for manufacturing a hot-rolled sheet, comprising hot-rolling an aluminum sheet in the presence of the aluminum sheet hot-rolling oil according to claim
 5. 